Nearest planetary system boasts two asteroid belts

时间：2017-06-07 05:00:02166网络整理admin

By Rachel Courtland The nearest known planetary system to Earth sports two asteroid belts, a new study suggests. The relatively young system could offer clues about how the solar system formed and might be the ideal place to look for the faint glint of an Earth-like planet. The belts were found in orbit around the nearby star Epsilon Eridani, which sits just 10.5 light years from Earth. The star boasts a planet that orbits once every 7 years and weighs about 60% the mass of Jupiter. Astronomers have also previously detected a far-out ring of icy material around the star, similar to our own Kuiper belt. Now, two rocky asteroid belts have been found much closer to the star, a new study suggests. Dana Backman of the SETI Institute in Mountain View, California, and colleagues caught the warmer glow of the two belts using NASA’s Spitzer Space Telescope, which images objects at infrared wavelengths. Epsilon Eridani’s inner belt is similar to the solar system’s own asteroid belt, which sits between Mars and Jupiter. The ring of debris sits 3 astronomical units (where 1 AU is the Earth-Sun distance) away from the star, and seems to be composed of silicon-based minerals. The star’s one known planet may orbit just beyond this ring. A second belt, which sits 20 AU from the star, holds 20 times more material, weighing in at roughly the same mass as the Moon. The previously known icy ring sits between 35 and 90 AU from Epsilon Eridani. This cometary belt is roughly 100 times more massive than the Kuiper belt that lies beyond Neptune’s orbit in our own solar system. Two other planets, between the size of Neptune and Jupiter, might also orbit Epsilon Eridani beyond its outer asteroid belt. One might have helped carve the outside edge of the outer asteroid belt, and the other might orbit just inside the star’s icy ‘Kuiper’ belt. Smaller planets could also be lurking inside Epsilon Eridani’s inner asteroid belt. “I would put money on there being an Earth-like planet in the space between the inner asteroid belt and the star,” Backman told New Scientist. The star is close enough that an Earth-like planet might be directly imaged with future telescopes, such as the Terrestrial Planet Finder Interferometer, a proposed orbiting array of telescopes currently being considered by NASA. The system might “be the first one where you could point to a pale blue dot and say, ‘There’s the Earth,'” Backman told New Scientist. Epsilon Eridani is only 850 million years old, about 20% the age of the Sun. As a result, it sheds light on what the solar system might once have looked like, before most of its debris was swallowed by the Sun or cast far away, says team member Massimo Marengo of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Those insights could help refine models of how solar systems form,